JPH0248894B2 - DENSHISHASHINHEIBANINSATSUGENBANYOSHIJITAI - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a support for an electrophotographic printing original plate. In general electrophotographic printing plates, an under layer is coated on the surface of a base paper support, and a photosensitive layer (photoconductive layer) of a zinc oxide/resin dispersion system is coated on top of this either directly or through a water-resistant layer. Furthermore, if necessary, a conductive treatment layer (back layer) is provided on the back surface of the support. This type of printing original plate is charged, exposed to light, developed, and heat-fixed using a heat source such as an infrared heater to become a printing original plate, but in the conventional version, the image area is black toner and the non-image area is a non-black toner. Due to the colors (pink, white, blue, purple, etc.), during heat fixing, a phenomenon occurs in which the black image area absorbs more heat and the non-image area has less heat absorption ability. A difference in heat shrinkage occurs in the non-image area, and distortion due to the shrinkage occurs in the image area, especially around the solid image. When printing starts, this distortion causes the original plate to be pressed between the master cylinder and the blanket cylinder, causing wrinkles in the areas where the distortion occurs, making printing impossible or causing the printed image to become a double image.
This was a fatal flaw as a master plate for lithographic printing. An object of the present invention is to provide an original plate for electrophotographic lithography that has improved the above-mentioned drawbacks, and as a result of extensive studies, the present inventors have completed the present invention. That is, the support for an electrophotographic lithographic printing original plate of the present invention has carbon black contained in an emulsion resin alone or in a binder consisting of the resin and a water-soluble polymer resin on one or both sides of the base paper. It is characterized by the provision of a pulling layer. Conventional printing plate supports include those in which carbon black is added internally to the base paper, and those in which carbon black is included in the back layer. The printing elongation is remarkable, and the latter has the disadvantage that carbon black adhesion to the photosensitive layer tends to cause stains and deteriorate the photosensitive characteristics, and carbon black is almost always used as a low-resistance processing agent. According to the present invention, by providing an undercoat layer containing carbon black as a main component on one or both sides of the base paper, it is possible to prevent distortion due to heat shrinkage and provide a printing base plate with extremely excellent durability. . Further, the present invention will be explained in detail based on the attached drawings. FIGS. 1A and 1B are schematic diagrams of a printing original plate using the support of the present invention. In the figure, 1 is the support base paper;
2 is the sublayer, 3 is the back layer, 4 is the under layer,
5 is a water-resistant layer (provided if necessary), 6 is a photosensitive layer, Fig. 1-A shows the case where the subbing layer 2 is provided on one side (surface) of the base paper, and Fig. 1-B shows the case where the subbing layer of 2 is provided on one side (surface) of the base paper. The case where it is provided on both sides is shown. The most distinctive feature of the present invention is the provision of an undercoat layer whose main component is carbon black. By subbing carbon black, it is possible to make full use of the light absorption ability of carbon black, and it brings out characteristics that other black pigments and dyes do not have. In addition, the difference in heat shrinkage between the image area and the non-image area when carbon black undercoating is applied is very small compared to conventional originals without undercoating, and there is no distortion around the image area at all. Therefore, an excellent original plate can be obtained without wrinkles during printing. An emulsion resin is used as a binder for the undercoat layer. Specific examples of emulsion resins include acrylic ester resins, vinyl acetate resins, vinyl chloride resins, styrene-butadiene copolymers, methyl metabutadiene copolymers, alkyd resins, phenolic resins, and epoxy resins. Emulsion resins have excellent water resistance, but it is also possible to use emulsion resins and water-soluble polymer resins together, and in this case, continuous film formation and organic solvent resistance can be improved. . Specific examples of water-soluble polymer resins include polyvinyl alcohol (PVA), starch, gum arabic, casein, sodium alginate, carboxymethyl cellulose, methyl cellulose, etc. The water-soluble polymer resin in the binder is preferably 50% or less. . Further, the amount of carbon in the undercoat layer is 20% or less, preferably 10% or less; if it exceeds 20%, it becomes difficult to suppress printing elongation due to penetration of dampening water during printing. Incidentally, as shown in FIG. 1, the difference in the occurrence of wrinkles is different when the undercoat layer is provided on one side of the base paper and when it is provided on both sides of the base paper. The former has a slight fixing distortion (kottling) compared to the latter, and the latter has a slight printing elongation distortion compared to the former. However, the objectives of the present invention are to accomplish both. Next, the back layer 3 is formed of a pigment-dispersed resin layer containing a cationic organic conductive substance or a resin layer containing no pigment. As the resin (binder) which is one of the constituent components of the back layer, a conventionally used water-soluble polymer resin or emulsion resin as described above can be used. When a suitable amount of pigment is added to form the back layer, examples of the pigment include inorganic pigments such as calcium carbonate, clay, talc, titanium oxide, and zinc oxide. The under layer of No. 4 uses the above-mentioned emulsion resin and water-soluble polymer resin as a binder, and optionally contains the above-mentioned inorganic pigment and a polymer electrolyte (for example, a quaternary ammonium-based polymer conductive agent) as a conductive agent. It is formed by mixing. The water-resistant layer 5 is provided as necessary, and is formed of a self-crosslinking type, thermosetting type emulsion resin, or a solvent type crosslinking type, thermosetting type resin. The photoconductive layer (photosensitive layer) No. 6 is the same as the photoconductive layer in general electrophotographic photosensitive materials, and includes, for example, polybutyl methacrylate, acrylate, polyvinyl chloride, polyvinyl acetate, polystyrene, silicone resin, Zinc oxide is dispersed in a lipophilic resin such as polyvinyl butyral or in a hydrophilic resin such as polyvinyl alcohol, carboxymethyl cellulose, casein, or gelatin. The solid content adhesion amount of each layer mentioned above is as follows:
1 to 10 g/m ² , back layer: 4 to 10 g/m ² , under layer: 2 to 6 g/m ² , water-resistant layer: 0 to 2 g/m ² , and photoconductive layer: 20 to 25 g/m ² . Examples are shown below. All parts are by weight. Example The composition shown below was adjusted to a solid content concentration of 20% with water to obtain a sample for an undercoat layer. (A) Carbon black (Dainichisei Chemical TB-710) 5 parts Acrylic emulsion (ROHM Hass HA-16) 95 parts (B) Carbon black (same as above) 10 parts Acrylic emulsion (same as above) 90 Part (C) Carbon black (same as above) 15 parts Acrylic emulsion (same as above) 85 parts (D) Carbon black (same as above) 20 parts Acrylic emulsion (same as above) 80 parts (E) Carbon black (Same as above) 25 parts Acrylic emulsion (same as above) 75 parts (F) Carbon black (same as above) 10 parts Acrylic emulsion (same as above) 70 parts PVA (Kuraray 105) 20 parts (G) Carbon Black (same as above) 10 parts Polyvinyl acetate (Sevian A-522 manufactured by Daicel) 80 parts PVA (Kuraray 105) 10 parts (E) Carbon black (same as above) 15 parts SBR (SK-72 manufactured by Takeda Pharmaceutical) 65 parts Starch (Nippon Shokuhin Kogyo MS-3600) 20 parts (I) Carbon black (same as above) 10 parts Polyvinyl acetate (Dial RSA-522) 90 parts (J) Carbon black (same as above) 15 parts SBR (same as above) 85 parts Next, the following composition was added to a fourdrinier machine until its dry weight was
A base paper of 110 g/m ² was prepared. LBKP (manufactured by Sanyo Pulp) 100 parts urea resin (Euramin P-1510 manufactured by Mitsui Toatsu) 2 parts sizing agent (Size Pine manufactured by Arakawa Forestry) 2 parts sulfuric acid band 4 parts Also, under layer coating liquid with the composition shown below. B and back layer coating solution C and D were adjusted. (B) PVA (same as above) 40 parts SBR (Asahi Dow DL-636) 60 parts (solid concentration 10%) (B) PVA (same as above) 100 parts (C) Clay (kaolinite) 150 parts Conductive agent (manufactured by Dow Chemical, ECR-77) 30 parts PVA (same as above) 70 parts (however, solid content concentration 30%) (d) Clay (same as above) 150 parts Conductive agent (same as above) 20 parts PVA (same as above) 40 parts SBR (manufactured by Dow Chemical, DC-636) 40 parts Furthermore, the following composition was added by emulsion.
A photoconductive layer coating solution was prepared by dispersing for 10 minutes. ZnO (manufactured by Sakai Chemical, Sazetsu (#4000)) 100 parts Silicone resin (manufactured by Shin-Etsu Chemical, KR-211)
20 parts Rose Bengal 0.1 part Toluene 100 parts Next, using the obtained base paper and coating solution for each layer, a book was prepared using the combinations shown in Table 1, except that the base paper and photoconductive layer were the same. A support for a printing original plate of the invention was produced. The manufacturing method is to form and coat an undercoat layer on one side (back side) or both sides of the base paper, then a back layer on the back side of the base paper, and an under layer on the front side using a wire bar, and then apply a supercalender treatment, followed by a photoconductive layer ( dry weight 20-25 g/ ^m2 ).

【table】

[Table] In addition, the following comparative example master plates were prepared. Comparative Example 1 An original plate was prepared in the same manner as in Example 1 except that no undercoat layer was provided. Comparative Example 2 In order to obtain a carbon-incorporated original plate, a base paper prepared in the same manner as above was used, in which 10 parts of carbon black was added to the support base paper composition, except that no subbing layer was provided. An original plate was produced in the same manner as in Example 1. Comparative Example 3 An original plate was prepared in the same manner as in Example 1, except that the following carbon black-containing composition was used as the back layer coating solution and no subbing layer was provided. Carbon black (same as above) 10 parts Conductive agent (same as above) 20 parts PVA (same as above) 70 parts (solid content concentration 20%, coating amount) (dry weight) 4 to 5 g/m ² ) Next, all the original plates obtained were evaluated as shown below. Carbon black adhesion stains on the photosensitive layer Fix the back layer on a flat table with the back layer facing up, and place the original plate with the photosensitive layer facing down on top of it.
Furthermore, a weight with an area of 10 x 10 mm and a weight of 2 kg was placed on it. The upper original plate was pulled and rubbed to evaluate the adhesion of carbon black to the photosensitive layer. Difference in heat shrinkage rate The plate was made using a Ricoh electronic printer S-3, and after heat fixing using a Ricoh autoprocessor FE-2, the heat shrinkage of the solid area and the heat shrinkage of the non-image area (background area) were measured with calipers. The difference in thermal shrinkage rate was calculated using the following calculation method. Solid area length before fixing: l ₁ , Solid area length after fixing:
l ₂ Length of non-image area before fixing: l ₃ , Length of non-image area after fixing: l ₄ , heat shrinkage rate of solid area (A) = l ₁ - l ₂ / l ₁ × 100 (%) Thermal shrinkage rate of the non-image area (B)=l ₃ −l ₄ /l ₃ ×100 (%), where (A)−(B)=the difference in the thermal shrinkage rate between the image area and the non-image area. Occurrence of wrinkles After making a plate of a 100 x 100 mm solid image original and thermally fixing it, wrinkles occur due to distortion during fixing. I checked to see if it existed. The lengths of the solid and non-image areas of the prints obtained in the test for difference in print elongation were measured using calipers, and the print elongation was determined using the following calculation method. The length of the solid area on the first page printed: l _A , The length of the solid area on the 1000th page printed: l _B The length of the non-image area on the first page printed: l _C , The length of the non-image area on the 1000th page printed: l _D When, the print elongation rate of the solid area (C) = l _B − _{l A} / l _A × 100 (%) The print elongation rate of the non-image area (D) = l _D − l _C / l _C × 100 (%) , (C)-(D)=difference in print elongation rate between image area and non-image area. Water Resistance 2 c.c. of water was dropped on the sample (on the subbing layer), wiped off with absorbent cotton for 1 minute, and evaluated by comparing it with a sample (before dropping). Number of Durable Printing Sheets After fixing the plate-made plate, it was etched and printed using a printing machine, and the number of sheets at which the photosensitive layer peeled off was determined. The results of each evaluation are shown in Table 2.

[Table] From the above results, the lithographic printing original plate support of the present invention is fully satisfactory overall, with very little distortion (wrinkles) and printing elongation due to heat fixation, and excellent durability. It was found that the system provides printed matter with a high level of quality. Comparative Example 1 had large distortions (wrinkles) and printing elongation due to fixing, Comparative Example 2 had large printing elongation and poor durability, and Comparative Example 3 had problems such as durability and carbon black adhesion staining. Ta.

[Brief explanation of drawings]

FIGS. 1A and 1B are schematic diagrams of a support for a lithographic printing original plate of the present invention. DESCRIPTION OF SYMBOLS 1... Support base paper, 2... Subbing layer, 3... Back layer, 4... Under layer, 6... Photoconductive layer (photosensitive layer).

Claims (1)

[Claims] 1 Electrophotographic lithographic printing characterized in that an undercoat layer containing carbon black in a binder made of an emulsion resin alone or a binder made of the emulsion resin and a water-soluble polymer resin is provided on one or both sides of a base paper support. Support for original plate.